Due to currently planned statutory provisions the particle emission of a combustion engine, in particular a diesel motor, has to be controlled before and/or after a particle filter during the driving operation, for example of a diesel particle filter (DPF). Furthermore a load prognosis of the diesel particle filter is required for a regeneration control in order to achieve a high system security and to be able to use cost-efficient filter material. Furthermore a regulation of the combustion features of the combustion engine can be provided on the basis of the information about the particle emission.
Particle filter provide however a limited storage capability for soot and have to be regenerated in certain intervals for the recovery of the purification effect. A controlling of the regeneration of the particle filter can either take place passively or actively. A high particle load of the filter causes an improperly high increase of the exhaust gas counter pressure.
In simple, actively operated procedures usually a driven route or an operating time of the combustion engine are taken as a basis for the implementation of the regeneration of the filter in fixed intervals. This typically takes place every 250 to 1000 km. at soot particle filters the regeneration takes place by an increase of the exhaust gas temperature up to typically 550° C. to 650° C. That can take place by measures in the mixture preparation of the engine or by post-motoric measures. Thereby an exothermal reaction is activated, which causes a burn-off of the soot and which regenerates the particle filter within a few minutes (for example 20 minutes).
Thus a system became known for example from EP 1130227 A1 for supporting the regeneration of a particle filter that is arranged in an exhaust gas area of a combustion engine, at which the exhaust gas temperature is increased for starting and maintaining the particle regeneration by adding hydrocarbons (HC) into the exhaust gas area. The increase of the exhaust gas temperature takes basically place by at least one fuel after injection into the combustion engine, which causes an increased HC-percentage, which reacts exothermally in an oxidization catalytic converter, which is arranged in the flow direction of the exhaust gas before the particle filter.
DE 10 2004 031 321 A1 and DE 10 2006 009 921 A1 suggest a procedure for metering a fuel into an exhaust gas duct of a combustion engine and a device for implementing the procedure.
Such a system, at which temporarily an exactly metered fuel amount is injected into the exhaust gas system for the regeneration of the particle filter, is also known under the name DEPARTRONIC by the applicant and is particularly provided for the use in utility vehicles with diesel engines. The HC-metering is determined from a cycle duration T and a duty cycle t1 for controlling a shut-off valve (SV) and a dosing valve (DV) depending on a pressure p1, measured with a pressure sensor, which is arranged in flow direction of the fuel in front of the dosing valve (DV), within a fuel metering device according to a polynomial procedure, in order to meter a desired HC-mass flow into the exhaust gas system, whereby the calculated values are send to the corresponding device driver of the shut-off valve (SV) and the dosing valve (DV). Thereby the following relation is the basis:Q=f(p, TV)  (1)
Whereby Q means the flow rate in g/min, p the difference pressure in bar above the dosing valve (DV) and TV the duty cycle in %. Corresponding power supply parameters (cycle duration T and duty cycle ti) for controlling the shut-off valve (SV) and the dosing valve (DV) arise from a polynomial of the typeT, ti=f(p, Δp2)  (2)
A further pressure sensor for determining a pressure p2 behind the dosing valve (DV) is currently used for the purpose of the diagnosis in the scope of the on-board-diagnosis (OBD).
It is currently disadvantageously that under practical conditions in the low pressure circuit (LPC) pressure peaks can occur, which can burst the first pressure sensor for determining the pressure p1. Furthermore such a pressure sensor increases the price of the current system.
It is therefore the task of the invention to establish a procedure, with which a pressure sensor could be waived for determining the pressure p1 and a value for the pressure p1 can be generated from other variables. It is furthermore the task of the invention to provide a corresponding device.